Mass storage systems continue to provide increased storage capacities to satisfy user demands. Photo and movie storage, and photo and movie sharing are examples of applications that fuel the growth in demand for larger and larger storage systems. A solution to these increasing demands is the use of arrays of multiple inexpensive disks. These arrays may be configured in ways that provide redundancy and error recovery without any loss of data. These arrays often are interconnected, and/or connected to a host using Serial Attached SCSI (SAS) communication links.
SAS is a communication protocol used to move data to and from computer storage devices such as hard drives and tape drives. SAS is a point-to-point serial protocol that displaces parallel SCSI bus technology in many computer systems and storage environments. SAS uses the standard SCSI command set. At the physical layer, the SAS standard defines connectors and voltage levels. The physical characteristics of the SAS wiring and signaling are compatible with and have loosely tracked that of serial ATA (SATA). SAS defines more rigorous physical signaling specifications as well as a wider allowable differential voltage swing intended to allow longer cabling. To characterize and/or debug SAS links, industry standard bit patterns (e.g., CJTPAT) may be used to generate and data transmitted via SAS links.